1. Field of the Invention
The present invention generally relates to communication networks, and more particularly, to an asymmetric encryption technique for the forward and return links of a communication network.
2. Discussion
Radio frequency-based communication networks are used throughout the world to transmit data between sources. Such communication networks include transponders that transmit the data between the sources. The bandwidth available on transponders is extremely limited. This is particularly true for satellite-based transponders. Since bandwidth is so limited, its use is very expensive.
In order to minimize costs and increase efficiency, it is desirable to impart as much data as possible into the bandwidth available on any given transponder. One technique employed to exploit available bandwidth is compression. Compressed data has a lower data rate and, as such, consumes less bandwidth. This saves money and increases efficiency.
A recent advancement in communication networks raises a competing interest with respect to minimizing bandwidth consumption. The increasing use of routable data creates a need for uncompressed data. Routable data includes routing information in the form of an addressee identifier. Although this routable data is typically multicast, addressees scan incoming data for their own address. Only data bearing the particular addressee's identifier is accepted and utilized. The remaining data is discarded.
The most commonly employed compression technique treats a data stream in bulk format. According to this technique, all of the data in the stream is compressed. Unfortunately, addressee identifying information is lost if it is compressed using such a bulk technique. As such, this data is no longer routable. Similarly, the most commonly employed encryption technique treats a data stream in bulk format so that all of the data in the stream is encrypted. Addressee identifying information is lost if it is encrypted using such a bulk technique.
Very recently, a new technique has been developed which divides a data stream into a header containing the addressee identifying information and a package containing the remaining information. According to this technique, the package is compressed while the header remains uncompressed. As such, the routing information is preserved while the remaining information is compressed. Advantageously, some compression is performed so as to increase efficiency and save money while the header is preserved to maintain routing ability. Further, a new encryption technique is available for encrypting the package while leaving the header unencrypted. As such, some encryption is performed so as to increase security while the header is preserved to maintain routing ability.
In an aeronautical mobile communication environment, the communications network is conveniently divided into a forward link and a return link. Most communicating over the forward link, i.e., ground to air, includes a single transmitting source and multiple recipients. The data transmitted on the forward link typically includes routing information. In contrast, most communicating over the return link, i.e., air to ground, includes multiple transmitting sources and a single recipient. Consequently, the data transmitted on the return link is typically devoid of routing information.
In view of the differences in the data transmitted in the forward and return links of an aeronautical mobile communications network, it would be desirable to provide an asymmetric compression method that employs packet compression on the forward link to provide some compression while maintaining routing information and bulk compression on the return link to maximize compression for efficient use of available bandwidth. It would also be desirable to provide an asymmetric encryption method that employs packet encryption on the forward link to provide some encryption while maintaining routing information and bulk encryption on the return link to maximize security.